Apparatus and method for handling and cooling plastic preforms

ABSTRACT

Apparatus for handling and cooling preforms, comprising a collection and translation element ( 2 ) provided with a plurality of receptacles ( 10 ) arranged according to a definite geometrical distribution pattern and adapted to accommodate a corresponding plurality of preforms ( 30 ), as well as a cooling element ( 3 ). Said collection element is displaceable from a preform loading position to several distinct positions, arranged above said cooling element, which is provided with a plurality of cups collected into a plurality of distinct, but similar geometrical distribution patterns that are translated with respect to each other in such a manner as to prevent them from interfering with each other. The collection and translation element can be selectively positioned in a number of such positions as to ensure that, in each one of said positions, the geometrical distribution pattern of the receptacles comes to be placed exactly above a specific geometrical distribution pattern of the cups, so that the preforms are capable of falling from the receptacles exactly into respective cups.

[0001] The present invention refers to a high-output, high-productivity plant for the production of plastic items, i.e. so-called “preforms”, and in particular the present invention applies in a preferred manner to machines adapted for moulding at the same time a plurality of such so-called “preforms”, that are intended for processing by blow moulding into appropriate final containers, especially plastic bottles.

[0002] The present invention represents a simplified variant of the invention described in the Italian patent application no. PN2000A000006 filed on Jan. 26^(th), 2000 by this same Applicant.

[0003] As a result, the description of the background of the invention, the state of the art and the problems connected therewith is set forth exhaustively in the above cited Italian patent application and shall not be repeated here for reasons of conciseness.

[0004] The solution proposed in the above cited patent application has actually turned out as being extremely effective in the production of preforms only, but not in the production of also finished blow-moulded containers. In other words, the solution disclosed in said patent application is characterized by a high capacity in cooling the preforms before the release thereof, and this is exactly the constraining element in a preform production plant.

[0005] Such a kind of solution can most obviously be used also in a so-called single-stage or single-step production plant, but in this case it should be duly taken into account that the preforms are of course required to be cooled down to a far lesser extent, since they must subsequently be again conditioned, i.e. brought up to a temperature of approx. 105° C. for blow moulding.

[0006] It therefore can be readily appreciated that such a solution appears to be rather exuberant if seen against the result which is actually aimed at. If the fact is then considered that such a solution turns ultimately out as being considerably complicated under all viewpoints and, therefore, quite cost-intensive and demanding, it can further be readily appreciated that it is not capable of allowing for an optimisation of a single-stage plant, which would rather receive a much greater advantage from the implementation of a less complicated solution, even if the latter would prove less adapted to cool down in a very short time the preforms as they come out of the injection mould.

[0007] The need also arises for another main drawback to be considered in this connection, i.e. the fact that the solution described in the above cited patent application is not generally adapted to be installed or integrated in modem single-stage plants owing to a lack of space, and this circumstance is such as to therefore be prejudicial to the utilization thereof in such kind of plants, even if its poor advantageous character in such particular application is left out of consideration.

[0008] Known from the disclosure in US RE. 33,237 is a plant for the production of generally hollow items of plastic material, but substantially of injection-moulded preforms, as this is explained in the first lines of the related description. Disclosed in this patent publication is in particular a construction solution that consists in providing a plate provided with appropriate cooling cups for respective preforms, and substantially characterized in that the two half-moulds that produce such preforms are alternately opened and moved away from each other to allow for the removal of the same preforms therefrom. The extent to which said half-moulds are moved away from each other is such as to allow for said plate with all its cooling cups to be directly introduced between said two half-moulds when these are fully opened apart.

[0009] This enables the preforms to be transferred directly from the injection mould to said cup-carrying plate, thereby cutting down on the operation time required and simplifying the construction of the plant itself.

[0010] This solution, however, can be only adopted in connection with plants that allow for such a kind of preform cooling plate to be introduced between the injection half-moulds, while it most clearly cannot be used in those plants which feature such construction and operation restraints as to practically exclude such a possibility.

[0011] It is therefore desirable, and it is actually a main purpose of the present invention, to provide a plant and a respective process which are adapted to implement and carry out a preform cooling-down phase under a sensible reduction in the length of the original cycle time, prove to be particularly efficient and advantageous when used in connection with a single-stage plant, are capable of doing away with the above described drawbacks, are reliable and capable of being easily implemented using readily available and, therefore, cost-effective materials and techniques.

[0012] Such an aim of the present invention, along with further features thereof, is reached in a plant that is made and operates as recited in the appended claims.

[0013] The present invention may take the form of a preferred, although not sole embodiment such as the one that is described in detail and illustrated below by way of non-limiting example with reference to the accompanying drawings, in which:

[0014]FIGS. 1 and 1a are a vertical projection view and a plan view according to the A-A section, respectively, of a plant according to the present invention, in a definite phase of operation thereof;

[0015]FIGS. 2, 2a . . . and so on through to FIGS. 11 and 11a are corresponding vertical-projection views and plan views according to the same section of the same plant, in successive different phases of operation thereof;

[0016]FIG. 12 is a more detailed top view of a component part of the plant according to the present invention;

[0017]FIG. 13 is a more detailed top view of a second component part of the plant according to the present invention.

[0018] With reference to the above listed Figures, a plant according to the present invention comprises:

[0019] a load-bearing structure 1,

[0020] a collection and translation element 2;

[0021] a plurality of receptacles 10 provided in said collection and translation element 2;

[0022] a cooling structure 3, provided with a plurality of cooling cups 6 adapted to accommodate respective preforms for pre-determined periods of time and then to release them on to other preform handling means.

[0023] For greater representation simplicity, in the FIGS. 1 through to 12 a said receptacles 10 and said cups 6 are symbolically represented only by the intersecting points of the axes determining the position thereof.

[0024] Said collection and translation element 2 is provided with means (not shown in the Figures) which make it capable of performing a horizontal motion that carries it alternately:

[0025] from a position inside the gap created between two opened horizontal half-moulds 23, 24 (see FIG. 12)

[0026] to a position situated outside such a gap and above said cooling structure 3 in such a manner as to enable the preforms 30 that are retained in said receptacle means to fall by gravity down into respective ones of said cups 6, in a manner and with means that will be described in greater detail further on,

[0027] to a third external all-out position (see FIG. 1 and FIGS. 6 through to 11), in which said element 2 is further displaced into such a position as to leave the space above said cooling structure completely free,

[0028] and, vice-versa, from this external all-out position again to the initial position between said two half-moulds.

[0029] Said receptacles 10 provided in said collection element 2 are preferably distributed according to the following geometric pattern: with reference to FIG. 12, which is a more detailed top view of said collection and translation element 2, said receptacles 10 are arranged along two rows A and B, in which they are aligned and equally spaced from each other.

[0030] In order to be able to better develop the continuation of his description, the overall geometry defined by the totality of said receptacles 10 in said collection element 2 will be defined as “distribution pattern”, while the preforms produced and at the same time introduced in said receptacles, and therefore arranged in the same so defined distribution pattern, are referred to as “cluster”.

[0031] In an advantageous manner, and to the purpose of making the most out of the available space, the two rows A and B include the highest possible number of receptacles 10 as allowed by the length of the rows themselves, owing to reasons that will explained in a greater detail further on.

[0032] With reference to FIG. 13, said cooling structure 3 comprises in turn two distinct and parallel rows 11, 12 of cups, in which the cups of both rows are generally arranged according to two distinct distribution patterns, each one of which is equal to the distribution pattern of said receptacles 10.

[0033] In other words, a first distribution pattern comprises both the cups identified by the numerals 100 through to 105 in the row 11, and, the cups identified by the numerals 200 through to 205 in the row 12.

[0034] Similarly, a second distribution pattern comprises both the cups identified by the numerals 300 through to 305 in the row 11, and the cups identified by the numerals 400 through to 405 in the row 12.

[0035] The row of receptacles in the element 2 can therefore be arranged selectively, using per se known means, above the cups comprised in one of the two just above described and illustrated distinct distribution patterns.

[0036] This most obviously enables the element 2 to load with respective preforms, and for successive cycles, all of the cups 6 arranged on said cooling structure 3, while each time unloading a successive cluster of preforms on to a different distribution pattern of cups by simply displacing and arranging in the appropriate position said cooling structure 3, in such a manner as to ensure that each distribution pattern of cooling cups 6 is enabled to alternately arrange itself under the distribution pattern provided in said collection element 2.

[0037] Since the task of said receptacles is to:

[0038] intercept the preforms released from the upper half-mould 23, collect said preforms in an orderly manner and orientate them vertically, i.e. with their neck portion or opening turned upwards,

[0039] transfer them above said cooling structure 3, and

[0040] finally let them fall into the respective cup, with the use of such means and techniques as generally known in the art, said receptacles and, more generally, said element 2 are provided with appropriate means that are adapted to selectively retain the single clusters of preforms falling down from above, and to release them downwards.

[0041] Also well-known to all those skilled in the art is the fact that, owing to reasons that shall not be recalled here due to them being so widely known, the centre distance between the preforms of a same cluster during injection moulding is quite different from and, in particular, quite smaller than the centre distance between the same preforms before and during the blow-moulding step.

[0042] The existence is further well-known of particular devices and operating modalities, which are generally known under the term of “pitch change” or “variable-pitch” facility and are adapted to widen the centre distance between preforms in order to reach the new pitch as required by the blow-moulding operation.

[0043] It therefore becomes advantageous for the possibility of implementing both the accelerated cooling of the preforms removed at the same time from the injection mould and the above cited pitch-change operation to be brought together into a single plant and related process.

[0044] Such a result can be reached in a plant as illustrated in particular in FIGS. 12 and 13, in which the collection element 2 contains two rows A and B of preform accommodating receptacles, in which the contiguous elements in the same row are separated from each other by a distance “L” that is the optimum one for the injection moulding of the preforms, whereas the cooling structure 3 comprises said two rows 11 and 12 of cups, in which however, in the row 11, the cups identified by the numerals 100 through to 105 are arranged alternately to the cups 300 through 305; similarly, in the row 12, the cups identified by the numerals 200 through to 205 are arranged alternately to the cups 400 through 405.

[0045] It will also be readily appreciated that, in order to really reach the desired result, said distance “L” between contiguous receptacles in a same row will be the optimum distance required in view of being able to produce preforms without any waste of unused space, whereas the distance “K” between the cups arranged in the same distribution pattern and contained in the same row, eg. the ones indicated at 100 through to 105, will be the optimum distance required as the desired spacing between the preforms in the blow-moulding phase, while the distance “M” between two adjacent cups, eg. between the cup 200 and the cup 400, and therefore belonging to the two different distribution patterns, can be determined partly arbitrarily, with the sole obvious constraint of keeping it sufficiently smaller than “K”.

[0046] Readily appreciated can on the other hand be also the fact that the means adapted to implement the above cited “pitch change” facility, i.e. the distribution of the preforms of a same cluster to the distinct distribution patterns on the cooling structure 3, are known to those skilled in the art, so that they shall not be described here.

[0047] The way in which the above described and illustrated plant operates will at this point be fully clear. Anyway, it can be summarized as follows:

[0048] in an initial phase of the process, the preforms 30 of a same sub-cluster are moulded in the half-moulds 23 and 24, which are subsequently opened apart, while the receptacles 10 of the element 2 are empty and the latter is still located outside said half-moulds 23, 24 (see FIGS. 1, 1a);

[0049] in a subsequent phase, the element 2 is inserted between said two half-moulds 23 and 24 in such a position as to enable the cluster of preforms, i.e. the preforms that are released from the upper half-mould at the same time, to fall down exactly into a corresponding number of receptacles 10 provided in the element 2 (FIGS. 2 and 2a);

[0050] in the next phase, the element 2 is transferred above said cooling structure 3 in such a manner as to enable the preforms of a same cluster, as previously loaded in the respective receptacles of the element 2, to get disposed above the cups of the first distribution pattern, i.e. from 100 through to 105 and from 200 through to 205, while at the same time undergoing the pitch change process to vary the centre distance therebetween (FIGS. 3 and 3a);

[0051] upon conclusion of the above mentioned phase, for reasons that will be explained in greater detail further on, only the preforms in the row B are allowed to fall down into respective cups 6 in the row 11 of the cooling structure 3 (FIGS. 4 and 4a) and, with reference to FIG. 15, into the cups identified with the numerals 100, 101, 102, 103, 104, 105;

[0052] in the following phase, and after a pre-determined period of time, only the preforms in the row A are in turn allowed to fall down into the respective cups 6 in the corresponding row 12 on the cooling structure 3 FIGS. 5, 5a) and, with reference to FIG. 15, into the cups identified with the numerals 200, 201, 202, 203, 204, 205;

[0053] subsequently (FIGS. 6 and 6a), the collection element 2 is withdrawn from its position above the cooling structure 3, which is shown with all of its cups filled with the respective preforms (also those identified with the numerals 300, 301 . . . 305, 400, 401 . . . 405, which have not been filled in the immediately preceding phases, so that they should be intended as having been loaded in a previous cycle).

[0054] In the meanwhile, the preforms that have already been inserted in the cups from 300 through to 305 and 400 through to 405 are regularly cooled down to the desired temperature value, and therefore for a predetermined length of time, after which the same preforms are picked up in sequence and, therefore, in the same order in which they had been inserted in the two distribution patterns comprised in the structure 3 of the given example.

[0055] Each cluster of preforms is then sent to the blow-moulding process using generally known means and methods.

[0056] In a preferred manner, these comprise conveying means 20, such as for instance a sliding conveyor belt, provided with appropriate pick-up means duly aligned and spaced at a distance “K” from each other so as to be able to exactly engage the preforms contained in alternate receptacles comprised in a single row of the structure 3.

[0057] Upon expiration of the period of time provided to allow, say, the preforms that had already been loaded in the respective cups 300, 301 . . . 305 in a previous cycle to properly cool down, said cooling structure 3 is raised with generally known means, so that the preforms in said cups are capable of being seized by respective pick-up means (not shown in the Figures, since well-known in the art) and carried away from said conveyor 20 (FIGS. 7, 7a).

[0058] Then, in order to load also the preforms 400 through to 405, as previously inserted in the respective cups, the structure 3 is:

[0059] lowered (see FIGS. 8, 8a);

[0060] translated sidewards by an extent which is equal to the distance between the rows 11 and 12, so that the row 12 gets now aligned with the conveying means 20 (FIGS. 9, 9a);

[0061] and finally raised again, so that also the preforms 400 through to 405 are seized by respective pick-up means and conveyed to the next processing station (FIGS. 10, 10a).

[0062] The structure 3 is then lowered again (FIGS. 11, 11a), so as to enable the working cycle to be restarted and repeated as illustrated in FIG. 1.

[0063] It should however be noticed that, during the subsequent phases, the preforms of a same cluster are inserted in the cups 300 through to 305 and 400 through to 405, which have just been cleared by the respective preforms, wherein said subsequent phases are used to appropriately cool down the preforms in the just loaded cups 100 through to 105 and 200 through to 205.

[0064] In order to be able to load said cups 300 through to 305 and 400 through to 405, considering that the cups between the two distinct distribution patterns are misaligned with respect to each other by a distance “M” as described above, the need arises for said cooling structure 3 to displace in the direction of the alignment of the rows 11 and 12 by an equal extent so that the preforms of the second loading are enabled to get correctly inserted in the respective cups of said second distribution pattern. To this purpose, means as generally known in the art are provided to impart a translatory, selectively actuatable motion to said structure.

[0065] Following said displacement, said element 2 is caused to move back into its initial position so as to allow for the loading of the cups belonging to the first distribution pattern.

[0066] As those skilled in the art will certainly have been able to notice, the cooling structure 3 substantially undergoes three types of motions, and namely:

[0067] an upward motion to enable the preforms, after the cooling thereof, to be seized by the respective pick-up means of the conveyor belt 20;

[0068] a sideward motion to successively bring a first row 11 and then a second row 12 into alignment with said pick-up means which are in turn provided in an aligned arrangement;

[0069] a displacement, in a direction parallel to the rows, by such an extent K as to enable in a first phase the cups in the first distribution pattern and in a subsequent phase the cups in the second distribution pattern to be loaded with respective preforms.

[0070] It will have certainly also been noticed that the circumstance of letting first the preforms of a row and then the preforms of the second row, belonging to a same distribution pattern, be loaded on to respective pick-up means, involves that different cooling times should be provided for each row, if the cups are filled at the same time.

[0071] However, since no cooling unevenness and, therefore, temperature unevenness is acceptable among the preforms in a continuous production environment and, in particular, in a single-stage plant, the need ensues for the cooling times to be levelled off. This is obtained by loading the row 11 with hot preforms at a certain instant, and then loading the cups of the row 12 with the respective preforms only after a pre-determined period of time has elapsed therefrom.

[0072] Such a delay can be obtained with various means that are generally known in the art, so that they shall not be dealt with here any further.

[0073] Those skilled in the art will therefore be able to readily appreciate that the described solution effectively enables a plurality of preforms, as appropriately gathered into a number of distinct distribution patterns, to be accommodated in a very limited space duly fitted for cooling down the same preforms. In fact, if the number of distribution patterns available on the cooling structure 3 altogether is indicated as n, and if the total duration of the cooling-down phase of the preforms is for technical reasons pre-set at T, it will be obvious that it is possible for a release of preforms to be obtained every period T/n.

[0074] It is therefore to such a same period T/n that the time, ie. duration, of the elementary cycle including preform injection, solidification and removal from the mould can be actually brought down to; and, therefore, the preform cooling-down time can be suitably reduced, this being allowed for by the possibility for preforms to be knocked out when still sufficiently hot for the subsequent blow-moulding phase, as compared with the solution and the constraints of the revolving-turret plant described in the afore cited patent application No. PN2000A000006. 

1. Apparatus for handling and cooling down preforms produced in an injection mould, as well as transferring said preforms to a subsequent work station for further processing said preforms, characterized in that it comprises: a collection and translation element (2), arranged horizontally, provided with an upper surface in which there are arranged a plurality of receptacles (10) organized according to a first definite distribution pattern and adapted to accommodate a corresponding plurality or clusters of preforms being ejected from an injection mould, a cooling element (3), in which said collection and translation element (2) is adapted to be displaced, with a preferably translatory motion, from a first preform loading position to selectively several distinct positions lying vertically above said cooling element (3), and is provided with means adapted to selectively retain and release the preforms in and from said respective receptacles, in which the surface of said cooling element is provided with a plurality of cups (6), each one of which is adapted to accommodate and cool down a respective preform and is univocally comprised in a second distribution pattern that may also not be identical to said definite distribution pattern od said receptacles (10), and in which said cooling element is provided with a plurality of distribution patterns that are mutually translated so as to prevent the respective cups (6) from interfering with each other.
 2. Apparatus according to claim 1, characterized in that it further comprises a device that is associated to said collection and translation element and is adapted to selectively modify said first distribution pattern of said receptacles so as to make it identical to said second distribution pattern, and to restore said first distribution pattern into its original form.
 3. Apparatus according to claim 1 or 2, characterized in that said collection and translation element is adapted to be selectively displaced into a plurality of distinct positions such that, for each one of said positions, the distribution patterns of said receptacles comes to lie exactly above a specific distribution pattern of said cups, so that the preforms released from said receptacles are capable of inserting exactly in respective cups.
 4. Apparatus according to claim 3, characterized in that each one of said distribution patterns provided in said cooling element consists of a plurality of arrangements, preferably parallel rows (11, 12), of aligned cups, in which each one of said arrangement comprises an equal number of said cups.
 5. Apparatus according to claim 4, characterized in that said cups, associated to distinct distribution patterns and arranged along a same row, are arranged alternately with respect to each other.
 6. Apparatus according to any of the preceding claims, characterized in that said collection and translation element (2) is adapted to move alternately with a rectilinear translatory motion between a first position, which is preferably situated between two injection half-moulds (23, 24) in the opened condition thereof, and a second position that lies substantially above said cooling element (3).
 7. Apparatus according to claim 6, characterized in that said cooling element (3) is adapted to selectively perform following three types of displacement motions: a first displacement, in a direction parallel to the rows, by such an extent (K) as to enable in a first phase the cups in a first distribution pattern and in a subsequent phase the cups in a second distribution pattern to be loaded with respective preforms; a second displacement in a transverse direction with respect to said first displacement to alternately bring a first row (11) and then a following row (12) into alignment with appropriate pick-up means (20) which are in turn aligned according to the same direction as said rows; a third upward displacement to enable the preforms, as inserted in respective cups, to be seized by respective pick-up means.
 8. Apparatus according to claim 7, characterized in that said three types of displacement motions are rectilinear and mutually orthogonal, and that said third displacement motion is oriented vertically upwards.
 9. Method for cooling plastic preforms carried out in an apparatus according to any combination of the preceding claims, characterized in that said method comprises following phases: injection moulding of a cluster of preforms (30) in appropriate half-moulds (23, 24), which are subsequently opened apart; insertion of a collection and translation element (2) between said two half-moulds and release of said preforms from the upper half-mould, so that the cluster of preforms, which are released at the same time from said upper half-mould, are able to fall down exactly into a corresponding number of receptacles (10) provided in said element (2); transfer of said element (2) to a position above a cooling structure (3) provided with a plurality of cooling cups (6), in such a manner as to enable said preforms to be carried above the cups of a first distribution pattern; release of said preforms so as to allow them to fall down into respective cups arranged in according to said first distribution pattern, possibly at successive moments; latching of a different sub-cluster of preforms, inserted in cups of said cooling structure (3) that are arranged according to a second distribution pattern, on to a conveying means (20) provided with appropriate, preferably aligned pick-up means, in which such a latching may possibly occur at successive moments and by means of a vertical displacement and possibly a horizontal translation of said cooling structure (3). 